The subject-matter of the invention relates to a method and to a sheet metal pack for manufacturing a honeycomb body with a large number of fluid permeable channels.
Metallic honeycomb bodies are known which are used as catalytic converter supporting bodies. Such a honeycomb body is composed of a large number of at least partly structured sheet metal layers. Numerous examples of the configuration of a honeycomb body are known from, for example, U.S. Pat. No. 4,923,109, International Patent Disclosure WO 90/03220, Published, European Patent Application EP 0 322 566 A1 and International Patent Disclosure WO 94/01661. International Patent Disclosure WO 97/00725 deals with the manufacturing of a honeycomb body with a large number of fluid permeable channels made from a large number of at least partly structured layers. This reference proposes that at least one stack of a plurality of at least partly structured sheet metal layers is layered up. Each stack is folded over on itself about a bending line in order to construct a sheet metal pack. Each sheet metal pack is disposed in a mold that has a contour corresponding to the external shape of the honeycomb body to be manufactured. Each stack is held by a looping device disposed in a central area of the mold. All the stacks are subsequently looped into a honeycomb body by rotation of the looping device relative to the mold. The honeycomb body prepared in this manner is subsequently fitted into a casing tube. A further method for manufacturing a honeycomb body is known from International Patent Disclosure WO 97/00135.
In further manufacturing steps, the honeycomb body is brazed to the casing tube. With this, it is substantially the end areas of the individual sheet metal layers that are brazed to the casing tube. With honeycomb bodies manufactured in this way, there is the danger that by folding each stack over on itself and looping the stack into a honeycomb body, in the area where the individual sheet metal layers join the casing tube, some sheet metal layers are brazed to the casing tube pipe over a relatively large part of the periphery of the casing surface of the casing tube, while other sheet metal layers are only brazed to the casing tube over a relatively small section of the periphery. This type of joining of the honeycomb body to the casing tube carries the danger that the honeycomb body will be damaged because of its mechanical and thermal stressing. In particular, there is the danger that the brazed connection between individual sheet metal layers will be at least partially destroyed.
It is accordingly an object of the invention to provide a method and a sheet metal pack for manufacturing a honeycomb body with a large number of fluid permeable channels which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which makes more even forming of a brazed connection to the jacket pipe possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for manufacturing a honeycomb body with a large number of fluid permeable channels. The method includes the step of forming a plurality of stacks by layering up a plurality of sheet metal layers for each of the stacks, some of the sheet metal layers are at least partly structured sheet metal layers. Each of the stacks are folded about a bending line resulting in a plurality of sheet metal packs being formed such that each of the sheet metal packs has a curved first end area and a second end area opposite the first end area. The second end area has a first end section and a second end section. The first end section has a first end face forming a first angle with a central plane, the second end section has a second end face forming a second angle with the central plane. The first angle is smaller than the second angle. A mold having a central area and looping devices are provided. Each of the sheet metal packs is fastened to one of the looping devices and the looping devices are disposed in the central area of the mold. The looping devices are rotated relative to the mold for forming the sheet metal packs into the honeycomb body.
In accordance with the method according to the invention for manufacturing the honeycomb body with a large number of fluid permeable channels, it is proposed that at least one stack is formed from a plurality of at least partly structured sheet metal layers, which are layered up. Afterwards, each stack is folded over on itself about the bending line to form the sheet metal pack such that the sheet metal pack has a curved first end area and a second end area opposite the first end area. The folding over of the stack on itself to form the sheet metal pack is done such that the second end area is formed by a first end section and a second end section of the stack. The first end section has a first end face. The second end section has a second end face. The first end face and the second end face together form an end face of the second end area of the sheet metal pack. The end faces are inclined relatively towards one another. The first end face forms a first angle xcex1 with a central plane, which is formed for example by a central sheet metal layer of the sheet metal pack which is folded over on itself. The second end face forms a second angle xcex2 with the central plane. The angle xcex2 and the angle xcex1 are inclusive angles. The angles are selected such that the first angle xcex1 is smaller than the second angle xcex2. This is obtained in that during folding the sheet metal layers in the first end section are displaced substantially more greatly relative to one another than the sheet metal layers in the second end section. In principle, the second end area of the stack of sheet metal is configured asymmetrically.
Each sheet metal pack is then held by a looping device disposed in the central area of a mold and looped into a honeycomb body by rotation of the looping device relative to the mold.
Unexpectedly, it has been shown that by the implementation of the method according to the invention when forming the honeycomb body, the honeycomb body has relatively evenly distributed sheet metal layer end parts, viewed in the direction of the periphery, so considerably more even brazing of the honeycomb body to the casing tube is possible. Because the honeycomb body can be more evenly brazed, a greater degree of operational reliability of the honeycomb body can be obtained.
According to an advantageous further development of the method, it is proposed that during the folding of the stack a considerably greater relative displacement of the sheet metal layers is permitted in the first end section than in the second end section. It is proposed in particular that during the folding, the sheet metal layers of the stack of the second end section are substantially stationary. In this way, the second end section of the sheet metal pack substantially retains the original shape of the end section as the stack. Different sheet metal stacks can also be provided with differently configured end sections, according to the number of stacks of sheet metal which are used for forming a honeycomb body, and according to the shape of the honeycomb body to be provided. By a combination of different sheet metal packs and by appropriate formation of the second end sections during the folding of the stack, the operational reliability of a honeycomb body can be increased.
To simplify the manufacturing of the honeycomb body, it is also proposed that at least during the folding, the stack is held in at least one area between the second end section and the bending line. This can be done, for example, by clamping the stack by the second end section. The clamping can also be such that it allows a certain displacement of the sheet metal layers.
Preferably, the stack is formed in that the sheet metal layers are layered up such that the second end face of the stack of the second end section is substantially perpendicular to the longitudinal direction of the stack. In particular, three stacks of this type are used for forming a honeycomb body.
According to a further preferred configuration it is proposed that at least one stack is layered up from at least partly structured sheet metal layers, and the sheet metal layers are substantially completely overlapping.
According to a further advantageous implementation of the method it is proposed that at least two sheet metal packs are disposed in a mold. The curved end area of each of the sheet metal packs is disposed in a central area of the mold. Each sheet metal pack is directed radially outwards as is known, for example, from International Patent Disclosure WO 97/00725. The sheet metal packs are held by the looping devices. The sheet metal packs are disposed in the mold such that when viewed in a peripheral direction, the first end section alternates with the second end section. This configuration of the sheet metal packs in the mold has the advantages that bending of each of the sheet metal packs takes place in the same direction. In this way, a more even distribution of the ends of each of the sheet metal layers of the sheet metal pack is also obtained when viewed in the peripheral direction, with each sheet metal pack.
According to yet another advantageous implementation of the method, it is proposed that the direction of rotation of the looping device is selected so that each sheet metal pack is bent around a respective axis of bending which is substantially parallel to the bending line and adjacent to a section of an outer sheet metal layer lying between the second end section and the curved end area.
According to a further inventive concept, the sheet metal pack is proposed for manufacturing the honeycomb body with a large number of fluid permeable channels. The sheet metal pack is composed of a plurality of at least partly structured sheet metal layers that are layered up and are folded over on themselves about a common bending line. The sheet metal pack has a curved first end area and a second end area opposite the first end area. The second end area is formed by a first end section and a second end section. The sheet metal pack is distinguished in that the first end section has a first end face and the second end section has a second end face, wherein the first end face encloses the first angle xcex1 with a central plane, and the second end face encloses a second angle xcex2 with the central plane, wherein the first angle xcex1 is smaller than the second angle xcex2. A sheet metal pack thus formed is suitable in particular for manufacturing a honeycomb body. The sheet metal pack can be looped according to the implementation of the method known from International Patent Disclosure WO 97/00725 or from International Patent Disclosure WO 97/00135 with other sheet metal packs of suitable configuration to form a honeycomb body, wherein a honeycomb body is obtained which has sheet metal ends which are distributed particularly evenly in the peripheral direction, so that a relatively even brazed connection between the honeycomb body and a jacket tube can be produced. Preferably, the sheet metal pack is configured such that the second angle xcex2 is approximately 90xc2x0.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a sheet metal pack for manufacturing a honeycomb body with a large number of fluid permeable channels, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.